334 Saxton. — Contributions to the Life-history of 
nuclei are now found beside the lower male cell as shown in Figs. 30, 31, 
and 12. Soon after the stage of Fig. 30, the two sterile nuclei begin to 
disorganize. The male cells at the same time become hemispherical, and 
then gradually separate from one another and round out, eventually 
becoming almost egg-shaped (Fig. 31). The two male cells are always 
exactly one above the other in the tube. Occasionally the disorganized 
remains of the sterile nuclei may be found in the same tube with mature 
male cells, as shown in the figure, but more often no trace of them is left. 
That this stage is one very shortly before fertilization is indicated by the 
fact that another pollen- tube closely adjacent to the one figured was already 
empty, having fertilized two archegonia in contact with it. In Fig. 10 each 
of the two pollen-tubes shows one of its two male cells cut transversely. 
It is necessary here to correct another misstatement in Coulter and 
Chamberlain’s ‘ Morphology of Gymnosperms ’ : they assert, in regard to 
W iddringtonia , that ‘ the single pollen-tube penetrates the megaspore 
membrane, and . . . only after entering within the membrane does the 
generative cell divide ’, but the latter statement can only be attributed to 
a vivid imagination on the part of those authors, as, from the context, it is 
fairly clear that ‘ generative cell ’ was not written merely by a slip of the 
pen for ‘body cell ’. It is obvious from the description, and Figs. 17, 30, 
31, and 32, in my paper on the genus (20), to which reference is made, that 
the body cell has been formed long before the tube reaches the megaspore 
membrane, and that the only division which occurs after entering within 
the membrane is that of the body cell. 
At about this time it is noticeable that a good many ovules become 
abortive, and it seems clear that this is due in all cases to the pollen-tube 
failing to reach its normal position. It is sometimes found that the tubes 
never get beyond the nucellus ; in other cases they penetrate a little way 
into the prothallus, but not to the region of archegonium initials. As many 
as four tubes, extending various distances down the ovule, have been found 
in one series of sections, all showing the rather undersized body cell 
characteristic of abortive tubes. Apparently the body cell never divides in 
these abortive tubes. 
It is very rarely that any other abnormality is met with in a pollen- 
tube, but the case shown in Fig. 32 is of some interest. Reference has 
already been made to this tube as the one found in the same prothallus as 
that in which the archegonia of Figs. 13 and 14 were contained. It includes 
four nuclei and a good deal of cytoplasm. The lowest nucleus is slightly 
larger than the other three, while the latter are very close to one another in 
a common mass of cytoplasm. No other nuclei are present in the tube. 
It may be seen that the size and organization of these nuclei are very much 
the same as those of normal male cells. (All the later stages of the pollen- 
tube are drawn to the same scale.) The likely explanation seems to be 
